1. Field of the Invention
The present invention relates to cooling systems, and in particular to arrangements of unidirectional coolant flow control units for pressurized cooling systems.
2. Background Art
Many systems require cooling to function properly. Some systems accomplish cooling through the flow of a coolant through the system. A cooling system can use redundant coolant flow control units to achieve greater reliability. However, in some systems, if one coolant flow control unit fails, the flow of coolant through that control unit can reverse itself, causing the cooling system to fail and the entire system to overheat. This problem can be better understood by a review of cooling systems.
Many systems (e.g. general purpose computers, automobiles and nuclear reactors) use a coolant to cool the system. Coolants can be any of a variety of substances, including light water, heavy water, air, carbon dioxide, helium, liquid sodium, liquid sodium-potassium alloy, and hydrocarbons (oils). Such substances are good conductors of heat and serve to carry the thermal energy produced by the system away from the system. A system draws fresh coolant in through one or more coolant intakes. The coolant, then, passes over system components which require cooling. Heat transfers from the system components to the coolant, thus cooling the components. Then, the heated coolant is expelled through one or more coolant exhausts.
The flow of coolant is often driven by a pressure difference between the interior and exterior of the system. The pressure difference is created by a coolant flow control unit. In a negatively pressurized system, a coolant flow control unit forces coolant out through a coolant exhaust. The smaller amount of coolant in the system causes the pressure inside the system to drop. Thus, the pressure inside the system will drop below the pressure outside the system near one or more coolant intakes. The pressure difference forces fresh coolant into the system through one or more coolant intakes. The coolant intakes and exhausts are positioned so that coolant flows through the parts of the system which require cooling. Heat transfers from the system parts to the coolant, and the coolant carries the heat out of the system.
FIG. 1 illustrates a system which cools through a negatively pressurized cooling system. The coolant flow control unit (100) causes the pressure on the inside of the system (110) near the coolant exhaust (120) to be higher than the pressure on the outside of the system (130). As a result, heated coolant (140) is expelled from the system through the coolant exhaust. The decrease in the amount of coolant in the system causes the pressure inside the system near the coolant intake (150) to be lower than the pressure outside the system. Thus, fresh coolant (160) flows into the system through the coolant intake. The fresh coolant will flow from the coolant intake, over the vital system components (170) and to the coolant exhaust.
FIG. 2 illustrates a cooling system with redundant coolant flow control units. Coolant flow control units 1 (200) and 2 (210) cause the pressure on the inside of the system (220) near coolant exhausts 1 (230) and 2 (240), respectively, to be higher than the pressure on the outside of the system (250). As a result, heated coolant (260) is expelled from the system through coolant exhausts 1 and 2. The decrease in the amount of coolant in the system causes the pressure inside the system near the coolant intake (270) to be lower than the pressure outside the system. Thus, fresh coolant (280) flows into the system through the coolant intake. The fresh coolant will flow from the coolant intake, over the vital system components (290) and to the coolant exhaust.
Redundant coolant flow control units are used to improve system reliability in some applications where cooling is critical. If a coolant flow control unit fails in a negatively pressured cooling system with redundant coolant flow control units, the pressure inside the system near the coolant exhaust for that failed coolant is no longer higher than the pressure outside the system. Since other coolant flow control units continue to force coolant out of the system, the pressure inside the system near the exhaust for the failed coolant flow control unit is lower than pressure outside the system. Thus, the flow of coolant through the failed coolant flow control unit reverses.
The flow reversal allows coolant to enter the system through the coolant exhaust for the failed coolant flow control unit and leave the system through a coolant exhaust for a functioning coolant flow control unit without passing over any of the system components which require cooling. The coolant entering the system through the coolant exhaust for the failed coolant flow control unit increases the pressure inside the system. The pressure increase brings the pressure inside the system closer to being equal to the pressure outside the system. As a result, less coolant is drawn in through the coolant intakes. Less coolant flowing through coolant intakes causes less coolant to flow over system components which can results in the system components being insufficiently cooled. Thus, a failed coolant flow control unit may result in parts of the system being insufficiently cooled.
FIG. 3 illustrates a system with redundant coolant flow control units, in which coolant flow control unit 1 (300) has failed. Coolant flow control unit 2 (310) still forces heated coolant (320) out of the system through coolant exhaust 2 (330). As a result, the pressure inside the system (340) near coolant exhaust 1 (350) is lower than outside the system (360). Thus, fresh coolant (370) flows in through coolant exhaust 1. That fresh coolant can flow out through coolant exhaust 2 without flowing over the vital system components (380). Additionally, since the pressure inside the system is equalized by the flow of coolant through coolant exhaust 1, the pressure near the coolant intake (390) is close to equivalent inside and outside the system. Thus, the amount of fresh coolant flowing in through the coolant intake and over the vital system components is greatly reduced. This may result in the vital system components overheating and the system failing in applications that utilize redundant coolant flow control units.
The present invention is a method and apparatus for unidirectional coolant flow control unit for pressurized cooling systems. Pressurized cooling systems with multiple coolant flow control units encounter problems when one or more coolant flow control units fails. If one or more coolant flow control units fails, the flow of coolant through the failed coolant flow control unit reverses. Reversal of coolant flow through a failed coolant flow control unit results in reduced performance of the cooling system and/or an overheating of the system due to a lack of cooling over the vital components of the system.
The invention comprises a valve on a coolant flow control unit. The valve remains in the open position during normal function of the coolant flow control unit. However, if the coolant flow control unit fails resulting in a reversal of the flow, the valve closes. Thus, the cooling system performs better than prior art cooling systems in the event of a failure of one or more coolant flow control units.
In one embodiment, multiple improved coolant flow control units can be implemented wherein a flow of coolant enters one side of the system and exits the other side. In the even of a failure, the closure of the valve is caused by the shifting pressure within the system, which forestalls the cooling problems associated with prior art redundant coolant control flow systems. One embodiment of the present invention can be implemented in computer systems. Other embodiments of the present invention are used in other systems where a pressurized cooling system is required.